A pale, haggard- looking Mischa Barton arrived on the Manhattan set of her new TV series, appearing little like the stunning former star of “The O.C.”

The troubled 23-year-old ac tress showed up for work with wet hair, no makeup and an unlit cigarette dangling from her lips as she scurried to the downtown set of “The Beautiful Life.” She plays a supermodel struggling with personal problems in the series, produced by Ashton Kutcher.

Just days ago, Barton was described as being on a health kick as she worked out at a downtown Equinox gym and hired a personal trainer to regain her strength.

Barton moved to New York last month after suffering a nervous breakdown in California and spending 10 days as an involuntary admission at the psychiatric hospital of Cedar Sinai Medical Center.